Caster system for mobile apparatus

ABSTRACT

A mobile imaging device includes a base having at least one caster, a first drive mechanism that moves the system in a transport mode and translates an imaging component relative to the base in a scan mode, and a second drive mechanism that extends caster relative to the base to raise the base off the ground in the transport mode, and retracts the caster relative to the base to lower the base to the ground in the scan mode. A caster system for a mobile apparatus includes a base containing a housing and a caster, attached to the base, the caster having a wheel defining a wheel axis and a swivel joint defining a swivel axis and a pivot point defining a pivot axis, wherein the caster pivots on the pivot axis as the caster is retracted into the housing and extended out of the housing.

RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalApplication No. 61/791,509, filed Mar. 15, 2013, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND

Conventional medical imaging devices, such as computed tomography (CT)and magnetic resonance (MR) imaging devices, are typically fixed,immobile devices located in a discrete area reserved for imaging that isoften far removed from the point-of-care where the devices could be mostuseful.

It would be desirable to make these imaging devices mobile, so that theycan move to various locations within a hospital or other health servicesenvironment. This is difficult due to the size, weight and overallnumber of components required for making an operable imaging system, andeven a relatively small and compact imaging device, such as an x-ray CTscanner, can weigh upwards of 2500 lbs.

There is a need to improve the mobility of imaging systems withoutsacrificing image quality or adding significantly to the size and weightof the device.

SUMMARY

Various embodiments include a mobile imaging system that includes a basehaving at least one caster, a first drive mechanism that moves theentire system in a transport mode and translates at least one imagingcomponent relative to the base in a scan mode, and a second drivemechanism that extends the at least one caster relative to the base toraise the base off the ground in the transport mode, and retracts the atleast one caster relative to the base to lower the base to the ground inthe scan mode.

Further embodiments include a caster system for a mobile apparatus, suchas an imaging device, that includes a base containing at least onehousing for a caster and at least one caster, attached to the base, thecaster having a wheel defining a wheel axis and a swivel joint defininga swivel axis and a pivot point defining a pivot axis, wherein thecaster pivots on the pivot axis as the caster is retracted into thehousing and extended out of the housing.

Further embodiments include an imaging system that includes a basehaving a housing, at least one component that translates relative to thebase in a scan mode, and a cable management system in the housing andcomprising at least one cable that couples at least one of power anddata between the base and the at least one component that translatesrelative to the base, the cable management system having a first endconnected to the base and a second end coupled to the at least onecomponent that translates relative to the base and extends in a loopbetween the first end and the second end such that a leading edge of theloop travels at a lower speed than a speed at which the at least onecomponent translates relative to the base

Further embodiments include a method of imaging using a mobile imagingsystem comprising a base, a first drive mechanism and at least oneimaging component mounted to the first drive mechanism, where the methodcomprises retracting at least one caster relative to the base to lowerthe base to the ground, translating the at least one imaging componentrelative to the base to obtain images of an object located above thebase, extending the at least one caster relative to the base to raisethe base off the ground, transporting the imaging system by driving adrive wheel mechanically coupled to the first drive mechanism when thebase is raised off the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be apparentfrom the following detailed description of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a side view of a mobile imaging system with a drive wheel andcasters extended and the base of the system raised off the floor.

FIG. 2 is a side view of the mobile imaging system with the drive wheeland casters retracted and the base lowered to the floor.

FIG. 3 is a bottom isometric view of the imaging system showing thedrive wheel and casters retracted and pads on the bottom surface of thebase that define a scan plane.

FIG. 4 is a side view of the mobile imaging system in a transport mode.

FIG. 5 is an isometric view of the mobile imaging system in a scan mode.

FIG. 6 is a top isometric view of the drive mechanism for an imagingsystem according to one embodiment.

FIG. 7 is an isometric view of the main drive assembly.

FIG. 8 is a bottom isometric view of the drive mechanism.

FIG. 9 is a rear isometric view of the drive mechanism.

FIG. 10 is a front isometric view of the drive mechanism.

FIGS. 11A and 11B are top isometric views of the main drive assembly.

FIGS. 12A and 12B are bottom isometric views of the drive mechanism.

FIG. 13 is a front view of the drive mechanism.

FIG. 14 is a side view of the drive mechanism.

FIG. 15 is a top view of the drive mechanism.

FIG. 16 is a cross-sectional view of the main drive assembly.

FIG. 17 illustrates a base and drive mechanism for mobile apparatusaccording to a second embodiment.

FIG. 18 illustrates a caster drive system.

FIG. 19A illustrates a caster system for mobile apparatus with castersfully extended.

FIG. 19B illustrates the caster system of FIG. 19A with casterspartially retracted.

FIG. 19C illustrates the caster system of FIG. 19A with casters fullyretracted.

FIGS. 20A-C illustrates a cable management system for a base with thebase not shown for clarity.

FIGS. 21A-C illustrate the cable management system with the base shown.

DETAILED DESCRIPTION

The various embodiments will be described in detail with reference tothe accompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.References made to particular examples and implementations are forillustrative purposes, and are not intended to limit the scope of theinvention or the claims.

Referring to FIGS. 1-5, a mobile imaging system 100 according to oneembodiment of the invention includes a mobile base 20, a gimbal support30, a gantry ring 40, and a pedestal 50. The system 100 includes imagecollection components, such as a rotatable x-ray source and detectorarray or stationary magnetic resonance imaging components, that arehoused within the gantry ring 40. The system 100 is configured tocollect imaging data, such as, for example x-ray computed tomography(CT) or magnetic resonance imaging (MRI) data, from an object locatedwithin the bore of the gantry ring 40, in any manner known in themedical imaging field. As shown in FIGS. 1-3 and 5, the pedestal 50 isadapted to support a tabletop support 60 that can be attached to thepedestal 50 in a cantilevered manner and extend out into the bore of thegantry ring 40 to support a patient or other object being imaged. Asshown in FIG. 4, the tabletop support 60 can be partially or entirelyremoved from the pedestal 50, and the gantry ring 40 can be rotatedrelative to the base 20, preferably at least about 90 degrees, from animaging position (FIGS. 1-3 and 5) to a transport position (FIG. 4) tofacilitate transport and/or storage of the imaging system.

As illustrated most clearly in FIGS. 3 and 5, the system 100 includes adrive mechanism 70. The drive mechanism 70 is mounted beneath the gimbal30 and the gantry ring 40 and within the base 20. The drive mechanism 70also comprises a drive wheel 71 that can extend and retract between afirst extended position (FIG. 1) to facilitate transport of the imagingsystem 100, and a second retracted position (FIGS. 2 and 3) during animage acquisition procedure (e.g., scan). The drive mechanism 70includes a main drive (described in further detail below) that is gearedinto the drive wheel 71 when the drive wheel 71 is in the first extendedposition (FIGS. 1 and 3) to propel the imaging system 100 across a flooror other surface, and thus facilitate transport and positioning of thesystem 100. According to one aspect, the drive wheel 71 is decoupledfrom the main drive when the drive wheel 71 is in the second retractedposition (FIGS. 2 and 3), thus preventing the system 100 from backdriving the main drive gearbox and motor during an imaging procedure.

As is illustrated in FIGS. 3 and 5, the base 20 is a sturdy, generallyrectilinear support structure. The base 20 includes a central openingextending lengthwise along the base, and the drive mechanism 70 ispositioned inside the central opening. As seen in FIG. 3, the bottom ofthe base 20 includes a plurality of pockets that contain retractablecasters 21. The casters 21 can be spring-loaded and biased to extendfrom the bottom of the base 20 when the system is raised off the ground,as shown in FIGS. 1 and 4. When the drive wheel 71 is retracted and thesystem 100 is lowered to the ground, as shown in FIG. 2, the casters 21are retracted into their respective pockets. In an alternativeembodiment, an active drive system, rather than a passive spring-basedsystem, can drive the extension and retraction of the casters in theirrespective pockets.

The top of the base 20 is shown in FIG. 5, and includes a pair ofparallel rails 23 running lengthwise on the top surface of the base, oneither side of the central opening of the base. During an imaging scan,the gantry 40, gimbal 30 and drive mechanism 70 translate along animaging axis relative to the base 20, pedestal 50 and patient support60. Bearing surfaces, which can be located on or attached to the drivemechanism 50 and/or gimbal 30, mate with the rails 23 to guide thetranslation motion relative to the base. The drive mechanism 70 caninclude a scan drive (described in further detail below) that drives thetranslation motion of the drive mechanism 70, gimbal 30 and gantry 40relative to the base 20.

The base 20 can be made compact and relatively lightweight to improvethe portability and usability of the system 100. Minimizing the heightand width of the base 20 minimizes interference with the operator's feetas the operator approaches a patient on the support table. A furtheradvantage of this embodiment is that the wheels, including drive wheel71 and casters 21, retract within the base during imaging, and thuscannot interfere with the operator. The drive mechanism 70 in thisembodiment is small and compact, and is generally hidden beneath thegimbal 30 and gantry ring 40 and positioned inside the central openingof the base 20, and advantageously does not interfere with the operatoror with the loading/unloading of a patient or patient support table.Positioning the wheels within the base also minimizes the risk of injury(e.g., running over a person's foot) during transport of the system. Itwill be further noted that in this embodiment, the width of the base 20tapers at the end of the base supporting the pedestal 50. An advantageof this design is that it allows a cart or shuttle to more easilyapproach the pedestal-end of the system 100 in order to transfer apatient support table 60 to the top of the pedestal 50 for imaging, orto remove the support table 60 from the top of the pedestal 50 followingimaging. The shape and size of the base 20 and pedestal 50 can bedesigned to mate with the cart to facilitate the interchange of patientsupport tables. Suitable patient support tables and transport carts areknown in the art, and examples are described in the JUPITER systembrochure (11/2008) from TRUMPF Medezin Systeme GmbH & Co. KG ofPuchheim, Germany, the entire contents of which are incorporated hereinby reference.

In one embodiment, the width of the base 20 is approximately equal to orless than the width of the patient support table. At its widest (e.g.,from the outside of the caster pockets), the base 20 can be less thanabout 25 inches wide, and can be around 22 or 23 inches wide. Thecentral opening of the base can be about 13 inches across, or any othersuitable dimension to accommodate the drive mechanism 70. The base 20 isgenerally less than about 6 inches in height when the system is loweredon the floor. The drive mechanism 70 is preferably very compact tomaximize the translation motion of the gantry ring 40 relative to thebase 20 and the support table 60. In one embodiment, the gantry ring 40can translate at least about 40 inches to 48 inches.

Conceptually, the imaging system 100 according to this embodiment can beconsidered to include two separate sub-assemblies. The firstsub-assembly is comprised of the base 20, pedestal 50 and patient table60. The second sub-assembly includes the drive mechanism 70, the gimbal30 and the gantry ring 40. This second sub-assembly includes most or allof the imaging components on the gantry ring 40, and is generally muchheavier than the first sub-assembly. By way of example, for an x-ray CTscanning system, the gimbal and gantry sub-assembly can weigh on theorder of 1400 to 1500 lbs., whereas the base/pedestal/table sub-assemblytypically only weighs about 1000 lbs. or less.

According to one aspect, the drive mechanism 70 supports the weights ofthe gimbal 30 and gantry ring 40 during imaging procedures as well asduring transport of the system. The base 20 and pedestal 50 aresupported on the casters 21 during transport of the system. Duringimaging, the base 20 is lowered and can be supported on the ground. Thedrive mechanism 70 is configured such that even when the drive wheel 71is retracted (FIGS. 2 and 3), the wheel 71 still contacts the ground andsupports the weight of the gantry and gimbal sub-assembly. The drivemechanism supports at least a portion of the weight of the gantry andgimbal sub-assembly—i.e. greater than 0% and up to 100% of the weight ofthese components. In one embodiment, at least 50% of the weight ofgantry and gimbal is supported by drive mechanism 71. In otherembodiments, at least 60%, at least 70%, at least 80%, at least 90% andmore than 95% of the weight of the gimbal and gantry sub-assembly issupported by the drive mechanism 71.

With this arrangement, the comparatively heavier weight of thegimbal/gantry sub-assembly does not need to be supported by the base ofthe system, which means the base can be made smaller and lighter forimproved portability. Further, since the imaging gantry is supported atall times at least in part by the drive mechanism, the gantry cantranslate a relatively long distance along the length of the base whileminimizing the possibility of beam deflection, which can result invariations of the scan plane and negatively effect image reconstruction.As shown in FIG. 3, the bottom surface of the base 20 includes at leastthree pads 25 that define a single imaging plane. When the base 20 islowered to the floor, the base 20 rests on the pads 25, which define asingle reference plane for the base, pedestal and table assembly, whichare fixed relative to the pads 25. The pads 25 maintain this referenceplane even when there are elevation differences in the floor. The rails23 of the base, upon which the gimbal and gantry translate, aresimilarly fixed in relation to the pads 25, and define an imaging plane,parallel to the reference plane, for the imaging components of thegantry. According to one aspect, the drive mechanism 70 includes asuspension system (described further below) between the drive wheel 71and the gantry that supports the weight of the gimbal and gantry andallows the drive wheel to conform to elevation differences in the floorwhile the gimbal and gantry translate in the imaging plane defined bythe rails, further minimizing deflection of the imaging plane path ofthe imaging components.

During transport mode, the drive mechanism 70 extends the drive wheel 71downward as shown in FIGS. 1 and 4, which causes the base 20 to raiseoff the ground and the casters 21 to extend. As previously noted, thecasters 21 can be spring-loaded to extend when the base 20 is lifted offthe ground, or alternatively, they can be actively extended by asuitable drive apparatus. The drive mechanism 70 can include asuspension drive (described in further detail below) to drive theextension and retraction of the drive wheel 71. During transport mode,the drive mechanism 71, along with the gimbal 30 and gantry ring 40, cantranslate to the approximate center of the base 20, as shown in FIG. 4,so that these heavier components are approximately centered between thecasters 21. This helps improve the balance and stability of the systemduring transport. The gimbal 30 and gantry ring 40 can be rotated intotransport position, as shown in FIG. 4. A pin system can lock the drivemechanism 70, gimbal 30 and gantry ring 40 in place relative to the base20 so that the entire system can be easily transported. The drivemechanism's main drive, which drives the drive wheel 71, can beservo-controlled, and the system 100 can be driven, in both forward andreverse directions, in response to a user input command. The suspensionsystem of the drive mechanism 71 can be an active suspension system, asdescribed below, which can aid in driving the imaging system 100 overuneven surfaces, such as thresholds and ramps. Steering of the systemcan be achieved by pivoting the system 100 around the centrally-locateddrive wheel 71, using the casters 21 for balance and support. A handleor other steering mechanism can be provided on the system (such as onthe gimbal, gantry, or pedestal) to assist in driving the system. Astrain gauge, throttle, button or other user-input mechanism located onthe system can provide servo-feedback down to the drive mechanism tocontrol the driving of the drive wheel 71. In one embodiment, shown inFIGS. 1-3 and 5, the system 100 can include a display system 31 thatincludes a camera on one side of the system and a display screen, suchas an LCD display, on the opposite side of the system that allows theoperator positioned behind the system to see obstacles in front of thesystem, which further assists the transport of the system. The system100 can include a collision detection system, such as an audio or visualrange-finder device, to further assist in transporting the device.

Turning now to FIGS. 6-16, a drive mechanism 70 in accordance with oneembodiment of the invention is shown. The drive mechanism 70 can includethree drive systems: a main drive assembly 73 that is coupled to anddrives the drive wheel 71 for transporting the imaging system, a scandrive assembly 75 for translating the imaging components relative to thesystem base during an imaging scan, and a suspension drive assembly 77that controls the extension and retraction of the drive wheel 71.

The main drive 73 is shown most clearly in FIGS. 7, 11A, 11B, and 16,and includes a motor 81, a sprocket 83 that can be connected by a drivechain 89 (FIG. 6) to the drive wheel 71, a gearbox 82, a sliding yoke84, and a brake mechanism 86. As noted above, the main drive 73 isengaged to the drive wheel 71 when the wheel is extended in transportmode, and is de-coupled from the drive wheel when the wheel is retractedduring an imaging mode. The engagement and disengagement of the drivewheel 71 is accomplished by the sliding yoke 84, which is connected to amain drive decoupling linkage 91 (FIGS. 12B and 13). As the drive wheel71 retracts and extends, the decoupling linkage 91, which can be arotating piston and sleeve assembly, causes the yoke 84 to reciprocate,as shown by the arrow in FIG. 7. This causes a sliding spline 85 (FIG.16), connected to the yoke 84, to move in and out of mating engagementwith the sprocket 83, thereby controlling the engagement anddisengagement of the drive wheel 71 from the motor 81 and gearbox 82.The yoke 84 and spline 85 can be spring-biased into a disengagedposition, and only when the drive wheel is in an extended position doesthe wheel 71 become engaged to the main drive.

The main drive 73 also includes a brake mechanism, which includes arotating brake disc 86, a spring-loaded brake rod 87, and a brakesolenoid 88. The brake disc 86 can be coupled to the sprocket 83. Thebrake rod 87 can be biased to extend beyond the brake disc 86, as shownin FIG. 7, which prevents the sprocket 83 and drive wheel 71 fromrotating. The brake mechanism thus functions similar to a parking brakein an automobile. When the solenoid 88 is energized, it drives the brakerod 87 to retract away from the brake disc 86, which is then free torotate along with the sprocket 83 and drive wheel 71. An importantsafety feature of this design is that if the imaging system 100 losespower, the brake rod automatically extends to stop the motion of thedrive wheel 71.

The scan drive assembly 75 is shown in FIGS. 6, 8-10 and 12A-13. Thescan drive assembly 75 drives the translation of the drive mechanism 70,gimbal 30 and gantry ring 40 relative to the base 20. In thisembodiment, the scan drive assembly 75 is mounted adjacent the maindrive assembly 73 and drive wheel 71. All of these components aremounted beneath the gimbal 30 and gantry ring 40 in a compact space,generally in the opening within the base 20. The scan drive assembly 75in this embodiment includes a motor 92 and a belt drive 93, which isshown most clearly in FIGS. 8 and 10. The belt drive 93 mates with abearing surface on the base 20 in order to effect the translation of thedrive mechanism, gimbal and gantry ring relative to the base. In oneembodiment, the belt drive 93 mates with a bearing surface, which can bea lip or rail (not shown), provided on an interior wall of the centralopening of the base 20 (FIGS. 3 and 5). A belt 94 is secured to thebearing surface and is looped through the belt drive 93, where it mesheswith a pulley driven by the scan drive motor 92, as shown in FIGS. 8 and10. The rotation of the scan drive motor 92 thus causes the scan driveassembly 75 to traverse along the length of the belt 94, and therebytranslate the gantry, gimbal and drive mechanism relative to the base.The belt drive 93 can be servo-controlled, with a linear encoder device,and have substantially zero or minimal backlash, to provide precise,controlled fine-scanning of the imaging components relative to the baseand patient support table. Any suitable configuration for achievingtranslation using a scan drive disposed within the drive mechanism canbe employed.

The suspension drive assembly 77 is shown most clearly in FIGS. 6, 8-10,and 12A-15. The suspension drive assembly comprises a motor 95 andgearbox 96 that drive the rotation of a lead screw 97. A lead screw nut98 translates with the rotation of the lead screw 97, as indicated bythe “nut travel” arrow shown in FIG. 6. The lead screw nut 98 ismechanically coupled to a pair of rail carriages 99, so that thetranslation of the lead screw nut 98 causes the rail carriages 99 totranslate on a pair of rails 101 that are fixed to the upper plate 102of the drive mechanism 70, as shown in FIG. 8. The rail carriages 99 areeach connected to one end of a spring 103, which can be a gas spring, asshown in FIG. 8. The other end of each spring 103 is connected arespective swing arm 104 that can pivot with respect to the drivemechanism around an pivot axis 106. As can be seen in FIG. 8, forexample, the translation of the rail carriages 99 causes the springs 103to articulate with respect to the rail carriages 99 and the swing arms104, which in turn causes the swing arms 104 to pivot, as showngenerally by the arrow in FIG. 8. The drive wheel 71 is mounted betweenthe two pivoting swing arms 104, so that the translation of the railcarriages 99 and the resulting pivoting motion of the swing arms 104causes the drive wheel 71 to extend and retract relative to the upperplate 102 of the drive mechanism 70.

As can be seen in FIGS. 12A and 12B, the main drive 73 can be mounted tothe swing arms 104. In this way, as the rail carriages 99 translatecausing the swing arms 104 to pivot, the main driveengagement/disengagement linkage 91, which connects the upper plate 102of the drive mechanism 71 to the sliding yoke 84 of the main drive 73,acts on the sliding yoke 84 to selectively engage and disengage the maindrive 73 to and from the drive wheel 71. As previously discussed, in oneembodiment, the drive wheel 71 is engaged to the main drive 73 only whenit is in an extended position—i.e., when the swing arms 104, main drive73 and drive wheel 71 are pivoted down and away from the upper plate 102of the drive mechanism 70. When the drive wheel 71 is retracted—i.e.,the swing arms 104, main drive 73 and drive wheel 71 are pivoted upwardstowards the upper plate 102, the yoke 84 slides back to disengage themain drive 73 from the drive wheel 71.

It will be noted that when the drive wheel 71 is retracted, the base 20automatically lowers to the ground and rests on pads 25, as shown inFIGS. 2, 3 and 5. During an imaging scan, the weight of the gimbal 40and gantry 30 remains supported by the drive wheel 71, which is able tofreely-rotate as the gimbal and gantry translate on the rails 23 of thebase. One advantage of this configuration is that the heavy gimbal andgantry ring assembly can be easily moved manually relative to the base,such as may be required in order to quickly access a patient during anemergency situation.

The springs 103 function as a suspension system between the drive wheel71 and the gimbal 30 and gantry ring 40, which are supported by thedrive wheel 71 during both transport and imaging modes. The springs 103can contract to allow the wheel 71 to conform to elevation differencesin the floor during an imaging scan, while the drive mechanism 70,gimbal 30 and gantry ring 40 translate on the base 20 during an imagingscan. This can greatly reduce or eliminate deflection of the scan planepath of the imaging components during the fine movement scan. Duringtransport of the system 100, the springs 103 can facilitate transport ofthe system over uneven surfaces, including door thresholds and ramps,for example. In one embodiment, the suspension system is an activesuspension system that can maintain a controlled force between the drivewheel and the floor. In this embodiment, the springs 103 and suspensiondrive assembly 77 can include an active servo-control system that cancontinually adjust the translation of the rail carriages to maintain asubstantially constant spring displacement, and thus maintain asubstantially constant force between the wheel and the floor. As shownin FIGS. 12A and 13, for example, an encoder 105 can be provided on atleast one of the swing arms 104 to measure the displacement of the swingarm 104 and spring(s) 103 relative to the upper plate 102. The encoder105 can provide a feedback signal to the suspension drive 77 to makecontinual fine adjustments and control the force between the wheel andthe floor.

The drive wheel 71 can comprise a suitable elastomeric material that israted to safely support the weight of the imaging components in thegimbal and gantry ring assembly. For example, the wheel can be rated tosupport about 1900 lbs. A softer durometer material for the wheel willprovide better grip and minimize the risk of slippage, but may not berated to support the required weights.

An advantage of the present drive mechanism 71 is that it is easilyaccessible for servicing and repair. For example, the drive wheel can beextended to raise the system off the floor and provide easy access toany components of the drive mechanism 71. If the drive mechanism 71needs to be removed, the system can be put on blocks, and the entiredrive mechanism can be taken out at once, such as by removing the upperplate of the drive mechanism from the bottom of the gimbal 30.

A drive mechanism 271 according to another embodiment is shown in FIG.17. The drive mechanism 271 may be similar to the drive mechanism 71described and illustrated previously in this document. The drivemechanism 271 may be located within an opening of a base 20. Anapparatus, such as a medical device (e.g., a diagnostic imaging device,such as an x-ray CT scanner or MRI device) may be mounted to the topsurface of the drive mechanism 271. In embodiments, the drive mechanism271 may be mounted to a gimbal 30 and gantry 40 containing imagingcomponents, as described above, and may support the weight of the gimbal30 and gantry 40. The drive mechanism 271 may include a main drivewheel, such as wheel 71 described and illustrated previously in thisembodiment. (The main drive wheel is not visible in FIG. 17). The drivemechanism 271 may include a main drive 73 (see FIGS. 7, 9, 11A-11B,12A-12B, 14 and 16) that is coupled to and drives the main drive wheelfor transporting the apparatus (e.g., imaging system). The drivemechanism 271 may also include a scan drive (not visible in FIG. 17),such as scan drive 75 described and illustrated previously in thisdocument, that translates the drive mechanism 271 and any componentsmounted to the drive mechanism (such as a gimbal 30 and gantry 40)relative to the base 20. The translation may be via rails 23 on the base20, as described above. The base 20 may be a rigid support structure(e.g., cast aluminum reinforced by a structural material, such asstructural aluminum) and may include casters 21 for transport of thesystem when the base 20 is raised off the ground, and pockets 224 intowhich the casters 21 may retract when the base 20 is lowered, asdescribed above. The base 20 may include, or have attached to it, acolumn area 250, which may be at one end of the base, and which maysupport a pedestal (i.e., patient column), such as pedestal 50 describedabove. Optionally, the column area 250 may be omitted, and the system,including the base, may be transported to a separate column or othersupport to perform an imaging scan. In such an embodiment of an imagingsystem, the system may be bi-directional in that the system can performa scan from either end of the system.

The drive mechanism 271 of FIG. 17 may be different from the drivemechanism 70 described above in that a suspension drive assembly 77 maybe omitted in the drive mechanism 271 of FIG. 17. The main drive wheel71 may be connected to the drive mechanism 271 via a suspension systemthat enables the drive wheel 71 to extend and retract relative to therest of the drive mechanism 271, as described above. The suspensionsystem may include a pair of springs, such as gas springs (one spring103 is visible in FIG. 17). The suspension system may be tuned to expectthe same downward force from the components mounted to the drivemechanism 271 (e.g., the gantry 40 and gimbal 30) as the drive wheel 71moves across the floor, so with any variation (i.e., a bump or dip inthe floor) the suspension system moves up and down (similar to a car).

In addition, the system of FIG. 17 includes an active drive mechanism223 in the base 20 that raises and lowers the base and may initiate theraising and lowering of the entire system. The drive mechanism 223 inthe base 20 may be coupled to the casters 21, and may cause the casters21 to extend and retract relative to the bottom surface of the base 20.In the embodiment shown in FIG. 17, the active drive mechanism 223 maycause the casters 21 to retract into their respective pockets 224 tolower the base 20 to the ground (e.g., during a scanning mode), and maycause the casters 21 to extend out from their respective pockets 224 toraise the base 20 from the ground (e.g., during transport mode). Thesuspension system of the drive mechanism 271 may be tuned to follow theposition of the base 20. For example, as the base 20 is raised off theground, it may push against the gimbal 30/gantry 40 assembly (i.e.,making this assembly appear lighter to the suspension system of thedrive mechanism 271), and the suspension system may be tuned to react tothis by extending the drive wheel 71 relative to the drive mechanism 271(i.e., so that the drive mechanism 217 and gimbal 30/gantry 40 assemblyare raised up from the drive wheel 71, which maintains contact with theground). Thus, the entire system may be raised from the ground, with thecasters 21 supporting the majority of the weight (e.g., more than 50% to100%, such as 90% or more) of the base 20 and any components mounted tothe base 20 (such as a pedestal and/or patient support/table), and thedrive wheel 71 supporting the majority of the weight (e.g., more than50% to 100%, such as 90% or more) of the drive mechanism 217 and anycomponents mounted to the drive mechanism (such as a gimbal 30 andgantry 40, including imaging components).

Similarly, as the base 20 is lowered to the ground via the active casterdrive mechanism 223, the components mounted to drive mechanism 271(e.g., gimbal 30/gantry 40 assembly) appear heavier to the suspensionsystem of the drive mechanism 271, and the suspension system may betuned to react to this by retracting the drive wheel 71 relative to thedrive mechanism 271 (i.e., so that the drive mechanism 217 and gimbal30/gantry 40 assembly are lowered towards the ground in conjunction withthe lowering of the base 20). Thus, the entire system may be lowered tothe ground, with the base 20 being supported by the ground and the drivewheel 71 supporting the majority of the weight (e.g., more than 50% to100%, such as 90% or more) of the drive mechanism 217 and any componentsmounted to the drive mechanism (such as gimbal 30 and gantry 40).

Thus, in the drive mechanism 271 of FIG. 17, a separate suspension driveassembly 77 for actively extending and retracting the drive wheel 71relative to the drive mechanism 271 may be omitted.

The active drive mechanism 223 for extending/retracting the casters 21may be any suitable mechanism for deploying and retracting the casters21. In some embodiments, the structure of the base 20 or overall systemrequirements may impose limitations on the design of the caster drivemechanism. For example, in an imaging system, such as a diagnostic(e.g., CT) imaging system, the height dimension of the base may belimited to a certain amount to ensure that the center of the imagingarea (e.g., isocenter of gantry 40) is at a certain height convenient topatients and/or medical personnel. For example, the center of theimaging area may need to be at a height of about 42 inches when thesystem is lowered, which may limit the height of the base to being lessthan a foot, such as about 5-8 inches. It may also be desirable toprovide a drive mechanism that fits within a compact space to helpdecrease the overall size and footprint of a mobile apparatus.

One embodiment of an active drive system 223 for extending/retractingthe casters 21 shown in FIG. 17 includes at least one drive mechanism225 (e.g., a motor) that is mechanically coupled to one or more casters21 via a linkage assembly 227. The drive mechanism 225 and linkageassembly 227 may be located within the base 20. Each caster 21 may havea separate drive mechanism 225 connected to it (e.g., one drivemechanism 224 and linkage assembly 227 for each caster 21 of thesystem). Alternatively, a single drive mechanism 224 may be connected tomultiple casters 21, including all casters 21 of the system, viasuitable linkages. In the embodiment of FIG. 17, a first drive mechanism225 is connected to two casters 21 on a first side 222 of the base 20via linkages 227, and a second drive mechanism (not shown in FIG. 17) isconnected to two casters on the second side 224 of the base 20 vialinkages.

The drive mechanism 225 may be operable to impart a motive force to oneor more casters 21 via the linkage assembly 227 to cause the casters 21to extend or retract relative to the base 20. In some embodiments, suchas shown in FIG. 17, the drive mechanism 224 may impart a forceprimarily along the length of the base (e.g., along the direction ofarrow 229), and the linkage assembly 227 may convert the force into aprimarily vertical force (e.g., along the direction of arrow 231) topush up or down on the casters 21 to extend and retract the casters 21relative to the base 20.

The caster drive system 223 can use one or more of a lead screw, a ballscrew, hydraulics, pneumatics or any other method or component to pushup and down on the casters 21.

An exemplary embodiment of a caster drive system 223 is shown in FIG.18. The caster drive system 223 may be located within one side of thebase 20, and a separate drive system 223 may be located in the oppositeside of the base 20. The caster drive system 223 in this embodimentincludes a pair of motors 225 a, 225 b that each rotate a lead screw 241a, 241 b through a gearbox 239 a, 239 b, and each lead screw goes into anut that drives a suspension system 243 a, 243 b (e.g., a springsuspension). In this embodiment, the suspension system 243 a on the leftis a different type of suspension system than the one on the right 243 bdue to variations in the weight supported at either end of the base 20.For example, one end of the base 20 may support a pedestal (column) andpatient table, and may thus require a suspension system with acomparatively higher spring rate. The springs for the suspension systemmay be, for example, steel springs, polyurethane springs, gas springs,etc.

In the embodiment of FIG. 18, each caster 21 gets pushed down via therespective suspension system, deployment linkage(s) 227 a, 227 b and apivoting caster arm assembly 245 a, 245 b when the motor 225 a, 225 brotates the lead screw 241 a, 241 b in a first direction. The casters 21get pulled up when the motor 225 a, 225 b rotates the lead screw 245 a,245 b in the opposite direction. Limit switches 247 a, 247 b may beprovided to determine when the caster 21 is fully extended/retracted,and thus stop the motor 225 a, 225 b. The caster drive system 223 mayalso provide additional structural support within the base 20 and mayhelp stiffen the base 20. An example of a caster 21 being retracted intoa pocket 224 of a base 20 using a caster drive mechanism 223 is shown inFIGS. 19A-C. The process may be reversed (i.e., the caster 21 may beextended from base 20) using the drive mechanism 223.

A caster drive mechanism 223 such as described herein may be used forlifting and lowering any mobile apparatus. If the apparatus is lightenough, all or part of the main drive 271 may be omitted, and the entireapparatus may be pushed on the casters 21.

FIG. 19A illustrates a caster 21 in a fully extended position. Thecaster 21 includes a wheel 241 mounted to a fork 243 having a centralwheel axis 253, and a swivel joint 245 mounted to the fork 243 thatenables the wheel 241 and fork 243 to rotate about a swivel axis 251relative to the base 20. This design may enable the wheel 241 to roll inany direction, and facilitates moving the system in any directionwithout changing its orientation. The caster 21 typically includes anoffset between the wheel axis 253 and the swivel axis 251. When thecaster is moved and the wheel is not facing the correct direction, theoffset causes the wheel assembly to rotate around the swivel axis 251 tofollow behind the direction of movement. If there is no offset, thewheel will not rotate if not facing the correct direction. The offsetdistance between wheel axis 253 and swivel axis 251 determines theradius over which the caster 21 may rotate relative to the system.

The size of the caster wheels 241 may reflect a tradeoff betweenproviding a compact system with a small footprint, and the requirementsof the system. To minimize the size of the system, smaller wheels 241may be preferred, however a certain minimum wheel size may be requiredfor practical or regulatory reasons. For a mobile imaging system, forexample, the wheels may need to have a minimum size for ease oftransport in the intended environment (e.g., to get over door jams, gapsin elevators, etc.). In various embodiments, the wheel 241 may have a 3″diameter.

For certain mobile system, it may be advantageous to minimize the widthof the system base. In the case of a mobile diagnostic (e.g., x-ray CTimaging) system as described above, it may be advantageous that the basenot be significantly wider than the patient table to enable easy accessto the patient, and in some cases, it may be desirable for the base tohave a width that is less than the width of the patient table to providea “toehold” area for medical personnel working over the patient table.

As shown in FIG. 17, the widest point of the base 20 (indicated byarrow, W), may be in the area of the “pockets” 224 into which thecasters 21 are retracted. The size of the pocket required to receive thecasters 21 within the base 20 so that the base may be lowered to theground is a function of the size of the caster wheel, as well as theoffset between the wheel axis and the swivel axis (i.e., the swivelradius of the caster). The larger the offset, the larger the swivelradius of the caster 21 and the larger the dimensions (e.g., diameter)of the pocket 224.

In various embodiments, a retractable and extendable caster system isprovided in which at least one dimension of the space (e.g., pocket 224)in the base 20 into which the caster 21 is retracted may be minimized byproviding a pivot point 247 on the caster 21 that enables the wheelassembly to pivot with respect to axis 255. The pivot point 247 may beconfigured to pivot the wheel assembly to reduce the offset distancebetween the wheel axis 253 and the swivel axis 251 as the caster 21 ispulled up into its respective pocket (e.g., the base 20 is lowered tothe ground). The pivot point 247 may further enable the wheel assemblyto pivot out to increase the offset distance between the wheel axis 253and the swivel axis 251 as the caster is extended out from itsrespective pocket (e.g., the base 20 is raised off the ground).

In one embodiment, shown in FIGS. 19A-C, the caster 21 may be retractedrelative to the base 20 until a portion 273 of the caster 21 contactsagainst a lip 257 of the pocket 224 (FIG. 19B). Both the lip 257 and thecaster portion 273 may be made of a durable material that provides arelatively low friction interface so that the caster portion 273 mayslide past the lip 257. As the caster 21 moves past the lip 257, the lip257 pushes against the caster portion 273, causing the caster 21 torotate on pivot point 247. FIG. 19C shows the caster 21 in fullyretracted position. The caster 21 has been rotated on pivot point 247 toreduce the offset distance between the wheel axis and the swivel axis.In this example, the wheel axis is almost directly beneath the swivelaxis when the caster 21 is in the retracted position. The caster 21 mayfit into a pocket having smaller dimensions, which may help in providinga small, compact device.

This embodiment can be used for any mobile apparatus attached to amoveable base structure, such as mobile medical devices (e.g.,diagnostic, imaging, surgical or other treatment devices), non-medicaltesting and imaging equipment, laboratory equipment, industrialequipment, transportation devices, information technology (IT)equipment, cargo, shipping, storage and transport equipment, and thelike.

FIG. 19C illustrates a port 280 which may be used carry power into thebase 20 and to the rest of the system, as well as to carry data (e.g.,via an Ethernet connection) between the system and an outside entity. Inthe case of a mobile imaging scanner, it may be advantageous to includeport(s) connecting the system to external entities in the base 20, whichis the only component that is stationary during a scan. The cablescarrying power and data to and from various points in the system mustthen pass through the base 20 to get to port 280. However, since spacein the base 20 is extremely limited, managing the power and dataconnections in the base can be challenging.

FIGS. 20A-C and 21A-C illustrates a method of cable management in thebase 20. FIGS. 20A-C illustrate the cable management system 301 with thedrive mechanism 70/271 in a first position in FIG. 20A (at a first end303 of the base 20 proximate a power/data port 280), at a secondposition in FIG. 20B (in the middle of the base 20, or “transport”position), and at a third position in FIG. 20C (at the opposite end 305of the base, proximate a mounting area 250 for a pedestal/column). Forclarity, the base 20 is not shown in FIGS. 20A-C. FIGS. 21A-C illustratethe cable management system 301 with the drive mechanism 70/271 in thesame positions as in FIGS. 20A-C, respectively, but from the oppositeside and with the base 20 shown.

As shown in these drawings, the cable management system 300 may includea cable chain 301 that houses a plurality of cables. The cables maycarry power and/or data between two sub-assemblies of a system, such asbetween the base 20 and the drive mechanism 70, 271 and a gimbal30/gantry 40 sub-assembly of a mobile CT scanner as described above,where one sub-assembly may move relative to the other. One end of thecable chain 301 may be fixed to the base, and the other end of the cablechain 301 may be fixed to a movable component (e.g., drive mechanism70/271). The cables and cable chain 301 may be located within a housingin the base 20, and may be protected by a structural cover 311 (seeFIGS. 21A-C), such as a sheet metal cover, that may prevent the cablesfrom getting stepped on or otherwise damaged. A splash guard 313 (seeFIGS. 21A-C) may prevent liquids from getting into the housing.

The housing may also contain bearing surface 317 of the base that mateswith the belt drive 93 of the drive mechanism 70/271 (i.e., Z-drive) inorder to effect the translation of the drive mechanism, gimbal andgantry ring relative to the base (see FIGS. 3, 5, 8, and 10, above). Abelt 94 (see FIGS. 8 and 10) may be secured to the bearing surface 317and may be looped through the belt drive 93, where it meshes with apulley driven by the scan drive motor 92, as shown in FIGS. 8 and 10.The rotation of the scan drive motor 92 thus causes the scan driveassembly 75 (see FIGS. 8 and 10) to traverse over the bearing surface317 along the length of the belt 94, and thereby translate the gantry40, gimbal 30 and drive mechanism 70/271 (which include a bracket member312 that connects the scan drive assembly 75 to the rest of the drivemechanism 70/271 as shown in FIG. 20C) relative to the base 20. The beltdrive 93 can be servo-controlled, with a linear encoder device, and havesubstantially zero or minimal backlash, to provide precise, controlledfine-scanning of the imaging components relative to the base and patientsupport table.

One end of the cable chain 301 may connect to the drive mechanism70/271, such as at the belt drive 93 of the drive mechanism, asdescribed above. A small gap 315 in the housing (see FIGS. 21A-C) mayenable cables to connect the rest of the drive mechanism 70/271 and upinto the gimbal 30 and gantry 40.

The cable chain 301 may be a flexible covering (e.g., plastic covering)that forms a loop within the housing. The cable chain 301 may form aloop as shown in FIG. 20A, with a first portion of the cable chain 301fixed to the base 20 extending along the top interior surface of thehousing, and a second portion, fixed to the drive mechanism 70/271,extending along the bottom interior surface of the housing (e.g., lyingover the belt 94 for the z-drive, as described above). As the drivemechanism 70/271 translates along the base 20, the leading edge of thecable chain 301 loop is configured to travel at a lower speed than thedrive mechanism (e.g., ˜½ the speed of the drive mechanism translation).The second portion of the cable chain 301 gets pushed up to the top ofthe housing in advance of the belt drive 93 of the drive mechanism70/271. At the end of travel (FIG. 20C) substantially all of the cablechain 301 extends along the top interior surface of the housing. Theprocess may repeat in reverse as the drive mechanism translates in theopposite direction.

While the invention has been described in connection with specificmethods and apparatus, those skilled in the art will recognize otherequivalents to the specific embodiments herein. It is to be understoodthat the description is by way of example and not as a limitation to thescope of the invention and these equivalents are intended to beencompassed by the claims set forth below. The foregoing methoddescriptions are provided merely as illustrative examples and are notintended to require or imply that the steps of the various embodimentsmust be performed in the order presented. As will be appreciated by oneof skill in the art the order of steps in the foregoing embodiments maybe performed in any order. Words such as “thereafter,” “then,” “next,”etc. are not necessarily intended to limit the order of the steps; thesewords may be used to guide the reader through the description of themethods. Further, any reference to claim elements in the singular, forexample, using the articles “a,” “an” or “the” is not to be construed aslimiting the element to the singular.

The preceding description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present invention.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the scope of theinvention. Thus, the present invention is not intended to be limited tothe aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A mobile imaging system, comprising: a basehaving at least one caster; a first drive mechanism that moves theentire mobile imaging system in a transport mode and translates at leastone imaging component relative to the base in a scan mode; and a seconddrive mechanism that extends the at least one caster relative to thebase to raise the base off the ground in the transport mode, andretracts the at least one caster relative to the base to lower the baseto the ground in the scan mode, wherein the base comprises at least onehousing for the at least one caster, and the at least one casterretracts into the at least one housing and extends out of the at leastone housing and the at least one caster comprises a wheel defining awheel axis and a swivel joint defining a swivel axis and a pivot pointdefining a pivot axis, wherein the at least one caster pivots on thepivot axis as the at least one caster is retracted into the at least onehousing and extended out of the at least one housing, the at least onecaster has a first offset distance between the wheel axis and the swivelaxis when the at least one caster is extended and a second offsetdistance between the wheel axis and the swivel axis when the at leastone caster is retracted, and the second offset axis is less than thefirst offset axis, and the at least one housing for the caster has atleast one dimension such that the at least one housing is not largeenough to receive the at least one caster when the at least one casterhas the first offset distance.
 2. The mobile imaging system of claim 1,wherein the at least one imaging component is raised away from theground in response to the second drive mechanism extending the at leastone caster relative to the base and the at least one imaging componentis lowered towards the ground in response to the second drive mechanismretracting the at least one caster relative to the base.
 3. The systemof claim 2, wherein the second drive mechanism generates a motive forcein a direction substantially along a length of the base, and a linkageapparatus translates the motive force to a substantially vertical forcethat extends or retracts the at least one caster.
 4. The system of claim2, further comprising a cable management system in the base that couplespower and/or data between the base and at least one component thattranslates relative to the base.
 5. The system of claim 4, wherein thecable management system comprises a cable chain having a first endconnected to the base and a second end connected to the first drivemechanism.
 6. The system of claim 5, wherein the base comprises ahousing and the cable chain is located in the housing and extends in aloop between the first and the second end, and the first drive mechanismtranslates relative to the base in the scan mode and a leading edge ofthe loop travels at a lower speed than a speed at which the first drivemechanism translates relative to the base.
 7. The system of claim 6,wherein the housing of the base comprises a bearing surface that mateswith a scan drive mechanism of the first drive mechanism for translatingthe at least one imaging component relative to the base in the scanmode.
 8. The system of claim 2, wherein the base comprises a centralopening and the first drive mechanism is located within the centralopening, and the at least one imaging component is located in a gantrythat is mounted above the first drive mechanism, and the weight of thegantry and at least one imaging component is supported by the firstdrive mechanism during the transport mode and the scan mode.
 9. Thesystem of claim 8, wherein the first drive mechanism comprises a maindrive geared into a drive wheel and a suspension system coupled betweena first portion of the first drive mechanism and the drive wheel, andthe suspension system is tuned to expect a given downward force on thedrive wheel from components of the system that are supported by thedrive wheel.
 10. The system of claim 9, wherein the suspension system isconfigured to raise the first portion of the first drive mechanism, thegantry and the at least one imaging component away from the drive wheelwhen the second drive mechanism raises the base from the ground.
 11. Thesystem of claim 9, wherein the suspension system is configured to lowerthe first portion of the first drive mechanism, the gantry and the atleast one imaging component towards the drive wheel when the seconddrive mechanism lowers the base to the ground.
 12. The system of claim2, wherein the at least one caster is one of a plurality of casters inthe base, and the second drive mechanism is one of a plurality of seconddrive mechanisms located in the base, each second drive mechanism of theplurality of second drive mechanisms operable to extend and retract atleast one caster of the plurality of casters.
 13. The system of claim 2,wherein the system is an x-ray CT imaging system.
 14. A mobile imagingsystem, comprising: a base having a plurality of casters; a first drivemechanism that moves the entire mobile imaging system in a transportmode and translates at least one imaging component relative to the basein a scan mode; and a plurality of second drive mechanisms located inthe base, each second drive mechanism operable to extend at least onecaster of the plurality of casters relative to the base to raise thebase off the ground in the transport mode, and to retract the at leastone caster relative to the base to lower the base to the ground in thescan mode, wherein each second drive mechanism of the plurality ofsecond drive mechanisms comprises a motor coupled to an actuator thatdrives the extension and retraction of at least one caster of theplurality of casters.
 15. The system of claim 14, wherein each of theplurality of second drive mechanisms comprises a suspension systemlocated between at least one caster of the plurality of casters and theactuator, wherein a spring force of the suspension systems varies basedon an amount of weight supported by the at least one caster coupled tothe respective suspension system.
 16. A caster system for a mobileapparatus, comprising: a base containing at least one housing for acaster; and at least one caster, attached to the base, the at least onecaster having a wheel defining a wheel axis and a swivel joint defininga swivel axis and a pivot point defining a pivot axis, wherein the atleast one caster pivots on the pivot axis as the at least one caster isretracted into the at least one housing and extended out of the at leastone housing, the at least one caster has a first offset distance betweenthe wheel axis and the swivel axis when the at least one caster isextended and a second offset distance between the wheel axis and theswivel axis when the at least one caster is retracted, and the secondoffset axis is less than the first offset axis, and the at least onehousing for the at least one caster has at least one dimension such thatthe at least one housing is not large enough to receive the at least onecaster when the at least one caster has the first offset distance.